1. Fields of the Invention
The present invention relates to a Light Emitting Diode bulb (LED bulb), and more particularly, to a three-stage power adjustable Light Emitting Diode bulb with adjustable resistances to have different output power.
2. Descriptions of Related Art
The conventional three-stage adjustable bulb 31 comprises a first Tungsten-filament 311 of lower power and a second Tungsten-filament 312 of high power located in the bulb 31. The circuit for the conventional three-stage adjustable bulb 31 is disclosed in FIG. 5. A three-stage switch 32 is cooperated with the three-stage adjustable bulb 31. The first switch of the three-stage switch 32 is connected to the first Tungsten-filament 311 and the second switch of the three-stage switch 32 is connected to the second Tungsten-filament 312. The third switch of the three-stage switch 32 is connected to the first and second Tungsten-filaments 311, 312 in parallel. When the users switch to the first switch of the three-stage switch 32, the first Tungsten-filament 311 of lower power is activated. When the users switch to the second switch of the three-stage switch 32, the second Tungsten-filament 312 of lower power is activated. When the users switch to the third switch of the three-stage switch 32, the first and second Tungsten-filaments 311, 312 are both activated to have the maximum output power.
However, the Tungsten-filaments consume significant electric power energy and have shorter life. The conventional three-stage adjustable bulb using Tungsten-filaments cannot change their luminous power according to practical needs.
The present invention intends to provide a three-stage power adjustable Light Emitting Diode bulb which has adjustable resistances to have different output power.